1. Field of the Invention
The present invention relates to memory devices. More specifically, the invention relates to memory devices that are in the class of memory cards that are rewriteable.
2. Description of the Related Art
With the development of data terminal devices represented by cellular phones, the importance of memory devices by which different types of data are stored has been increasing. For memory devices, semiconductor memory, hard disks, and the like are used primarily. Data stored in data terminal devices includes not only textual data such as that of schedules and address files but also image data that is recorded by digital cameras, music data that is distributed through the Internet or the like, and other types of data. For these reasons, an increase in the capacity of memory devices used in data terminal devices is being promoted.
With improvements in the performance of data terminal devices, it has become easier for a user to comfortably carry large amounts of data, and convenience in daily life has been increasing. On the other hand, leaking of data stored in memory devices is becoming a problem. Because the type of data that can be input to a data terminal device has been diversified, if a memory device is lost, there is a risk of personal information being leaked to a third party. Furthermore, when a data terminal device is discarded, unless the data terminal device is physically destroyed, data stored in a memory device is left remaining, and there is a concern that the data will be disclosed to the public by a third party who has malicious intent.
Consequently, in order that data not be leaked to a third party, protection of the data using a personal identification number or the like is being considered. For example, devices in which a retry counter that records the number of failed attempts at password verification of a memory card is provided and data is compulsorily deleted when the number of failed attempts reaches a given number are known (referring to Patent Reference Document 1).    Patent Reference Document 1: Japanese Published Patent Application No. 2005-011151